docs: clarify v10 strategy API docs

Author: gastonfournier

README.md

@@ -110,21 +110,17 @@ You can also **provide an [Unleash context](https://docs.getunleash.io/reference
 
 ### Activation strategies
 
-The Java client comes with implementations for the built-in activation strategies provided by Unleash:
+The Java client supports Unleash built-in activation strategies (such as `default`, `userWithId`, `gradualRolloutRandom`, `gradualRolloutUserId`, `gradualRolloutSessionId`, `remoteAddress`, and `applicationHostname`).
 
-- DefaultStrategy
-- UserWithIdStrategy
-- GradualRolloutRandomStrategy
-- GradualRolloutUserWithIdStrategy
-- GradualRolloutSessionIdStrategy
-- RemoteAddressStrategy
-- ApplicationHostnameStrategy
+As of v10, these built-ins are evaluated by the embedded Yggdrasil engine and are not exposed as public Java strategy classes in this SDK.
 
 Read more about the strategies in the [activation strategies reference documentation](https://docs.getunleash.io/reference/activation-strategies).
 
 #### Custom strategies
-You may also specify and implement your own strategy. The specification must be registered in the Unleash UI and
-you must register the strategy implementation when you set up Unleash.
+You may also specify and implement your own strategy. The specification must be registered in the Unleash UI and you must register the strategy implementation when you set up Unleash.
+
+You can also provide a `fallbackStrategy` via `UnleashConfig` if the client receives a strategy
+name it does not recognize.
 
 ```java
 Strategy s1 = new MyAwesomeStrategy();

v10_MIGRATION_GUIDE.md

@@ -16,6 +16,12 @@ The Bootstrapping interface now requires an `Optional<String>` to be returned ra
 
 The strategy interface has changed to only include the two methods `getName` and `isEnabled`. `isEnabled` now requires both a parameter map and an `UnleashContext`. This only affects users who are implementing custom or fallback strategies.
 
+Built-in strategy classes from `io.getunleash.strategy` (for example
+`GradualRolloutRandomStrategy`, `GradualRolloutUserWithIdStrategy`, and
+`GradualRolloutSessionIdStrategy`) are no longer part of the Java SDK public API in v10.
+
+These strategies are evaluated internally by Yggdrasil. There is no class-for-class replacement to import for built-ins; use the built-ins via Unleash configuration, and implement `Strategy` only for custom or fallback behavior.
+
 ## Events
 
 The following subscriber functions are no longer available: `togglesBackedUp`, `toggleBackupRestored`, and `togglesBootstrapped`. Subscribing to `featuresBackedUp`, `featuresBackupRestored`, and `featuresBootstrapped` respectively serves the same purpose. These subscribers no longer yield events that contain the full feature flag definition, instead, they expose a `getFeatures` method which returns a list of lightweight Java objects containing the feature name, the type of flag, and the project it's bound to.